Radially expandable stents are commonly used to restore and maintain the patency of body passages, particularly blood vessels. Such stents are provided in a reduced diameter state suitable for percutaneous insertion into the body passage through a catheter. The stent is typically maintained in the reduced diameter state until delivery into the body passage, whereupon the stent is expanded to an increased diameter state within the body passage to hold open the body passage. A catheter delivered balloon is typically used to expand the stent to the increased diameter state.
A biocompatible cover can be provided on the outer and/or inner surfaces of the stent to reduce tissue reactions associated with the expansion of the stent into contact with the walls of the body vessel. Such covers can adversely effect the expansion characteristics of the stent by increasing the deployment pressure necessary to deploy the covered stent to the expanded state. Such covers can also cause asymmetrical expansion of the stent or incomplete expansion of portions or all of the stent. Additionally, deployment of the stent to the expanded state can cause the stent cover to tear and delaminate.